1. Technical Field
The present invention relates to a lighting device which lights a discharge lamp, a lighting control device, an illumination device, and a projector.
2. Related Art
A projector including a light source, an optical modulator which modulates a flux of light emitted from the light source to form an image based on image information, and a projection optical device which projects the image has been known in the related art. In many cases, such a light source uses a discharge lamp such as an ultra high pressure mercury lamp in which a discharging space is formed with a pair of electrodes and discharging material sealed therein, where a lighting control device is employed to control lighting of the discharge lamp. A known example of such a lighting control device may include a lighting device which lights a discharge lamp by supplying lamp power to the discharge lamp, and a controller which controls driving of the lighting device (see U.S. Pat. No. 5,463,287).
The lighting control device disclosed in U.S. Pat. No. 5,463,287 includes a converting circuit which adjusts output current and output power, an inverter circuit which converts direct current (DC) into alternating current (AC), an igniter circuit, a transformer which includes a primary winding connected to the igniter circuit and a secondary winding connected to the inverter circuit, and a control circuit (microcomputer) which controls these circuits through a plurality of driving circuits. In such a lighting control device, when the control circuit outputs signals to the driving circuits, the igniter circuit supplies a high voltage ignition pulse to the primary winding of the transformer. Accordingly, a high voltage pulse generated in the secondary winding of the transformer is applied to the discharge lamp to start discharging of the discharge lamp.
However, in the lighting control device disclosed in U.S. Pat. No. 5,463,287, since the control circuit, the driving circuit, and the igniter circuit are connected by a control line, there is a possibility that a high voltage is applied to the control line, which may result in damage to the control circuit. Accordingly, there is a need to provide a measure against high voltages for the control circuit, which may lead to a complicated configuration of the lighting control device.